Monoclonal antibodies denominated MoAb GA733, raised against a human stomach adenocarcinoma cell line, have been extensively evaluated for the diagnosis and therapy of human gastrointestinal tumors. See, e.g. Herlyn, et al. Hybridoma, vol. 5, Suppl. 1, 1986, pp. S3-S10. GA733 antibodies bind to a variety of tumors of the gastrointestinal tract, including prostate, cervix, ovarian, bladder, lung, breast, colorectal, and pancreatic carcinomas. In addition, the GA733 antibodies bind in varying degrees to normal epithelial tissues.
GA733 antibodies have been shown to inhibit the growth of tumor xenografts in nude mice. (Herlyn et al., (1980) Cancer Res. vol. 40, pp. 712-721; and Herlyn et al., (1984) J. Immunol. Methods, vol. 73, pp. 157-167.) In addition, these antibodies have been used to obtain anti-idiotypic antibodies which bear the internal image of the GA733 tumor antigen. The anti-idiotypic antibodies, when used as an immunogen, were able to elicit in two species of animals anti-antiidiotype antibodies, which have a binding specificity similar to that of the original GA733 antibodies. (Herlyn, et al. (1986) Science, vol. 232, pp. 100-102.)
GA733 antibodies immunoprecipitate a 40 kd cell surface glycoprotein isolated from colorectal tumor cells. However, it is difficult to obtain sufficient quantities of tumor antigen for immunizations. Thus, there is a need in the art for a means of producing substantial quantities of tumor-associated antigens such as GA733 antigen. Further, there is a need for other antibodies which react with different epitopes on the GA733 antigen. Additionally, there is a continuing need for different tumor-associated antigens than those already known.